There has been known a technique using a film for forming or a transfer foil in which a member having a shape, which is not easily decorated by direct printing, is decorated by integrally connecting a printed film to the surface of the member.
It is proposed to use, as a conventional film for forming and a film for a transfer foil, a biaxially oriented polyester film (see, for example, Japanese Unexamined Patent Publication (Kokai) No. 06-210799). It is proposed to use a polyester film haying forming stress within a specific range and to use a polyester haying lower forming stress than that of a biaxially oriented PET for the purpose of improving thermoformability, particularly a copolyester (see Japanese Patent No. 3,090,911). However, in the method using a biaxially oriented polyester film, the biaxially oriented polyester film is insufficient in thermoformability against transfer to a member having a complicated shape. In the method using a copolyester, the copolyester is excellent in thermoformability but is inferior in heat resistance since it has a low melting point, and thus peel marks may occur in the mold releasing step. Also, smoothness of the surface of the film is deteriorated by a solvent, for example, ethyl acetate or methyl ethyl ketone, contained in a printing inks, thus causing a problem that printing defects may occur. A film having excellent mold releasability, printability and thermoformability has been required as compared with these films.
Thus, there is proposed a laminated film, which satisfies mold releasability, printability and thermoformability, obtained by laminating a polyester film having excellent thermoformability with a polyolefin film having excellent mold releasability and resistance to organic solvents (see Japanese Unexamined Patent Publication (Kokai) No. 2004-188708). However, this laminated film had a problem such as high production cost since it requires the step of laminating a polyester film with a polyolefin film and is inferior in recyclability.
It could therefore be advantageous to provide a polyester laminated film for forming, which satisfies mold releasability, printability and thermoformability aspects, and is also excellent in cost performance.